| Summary: | The cation exchange capacity (GEC) of soil is an important criteria for assessing soil fertility beside its use in soil
classification. Seven methods, namely, (1) BaCl2
- triethanolamine of BaCl2
- TEA (PH 8.2), (2) NH40Ac (PH
7.0) - leaching, (3) NH40Ac (PH 7.0) - shaking, (4) compulsive exchange method of Gillman (1979) (GECcd,
(5) modified compulsive exchange method of Gillman (1986) (CEC3, (6) Summation of Ca from method 5 with
1 M NH4 NO3 exchangeable Al (CECtotal and (7) summation of NH40Ac (PH 7.0) exchangeable bases with 1 M
KCl exchangeable Al (CECsum) were used to determine and compare the CEC values of five acid tropical soils.
All methods gave different CEC values which followed the order BaCl2 - TEA> NH40Ac shaking = NH40Ac
leaching> CECsum = CECto
tal > CECCE = CECB• Methods with pH conditions close to field situations gave much
lower CEC values than the buffered methods. The buffered methods generate charge on the variable-charge colloids,
thus resulting in inflated CEC values, while the unbuffered methods do not. There is a high correlation between
BaCl2
- TEA and NH40Ac (PH 7. 0) leaching method; CECCE and CECsum; and, CECB and CECtotal Amongst
the methods evaluated, the NH40Ac (PH 7.0) leaching is recommended in routine soil analyses for classification
purposes while CECsum is recommended for agronomic evaluation.
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